A preparation method of a temperature compensation filter and a temperature compensation filter

Abstract

The present invention relates to the field of microelectronics technology, and in particular to a method for preparing a temperature compensation filter, comprising the steps of plating a bonding area metal layer on a substrate, and overlaying photoresist on areas outside the bonding area metal layer; plating a thickened metal layer on the bonding area metal layer; stripping the overlaid photoresist; sputtering a temperature compensation film on the thickened metal layer and other areas; and flattening the temperature compensation film so that the thickened metal layer is exposed outside the temperature compensation film.

Description

Technical Field

[0001] The present invention relates to the field of microelectronics technology, and in particular to a preparation method of a temperature compensation filter and the temperature compensation filter. Background Art

[0002] The current manufacturing process for temperature-compensated SAW filters (TCSAW) involves first fabricating a metal interdigital transducer on a piezoelectric substrate, then growing or sputtering a thick layer of silicon dioxide to form a multilayer structure. The positive temperature coefficient of silicon dioxide compensates for the negative temperature coefficient of the piezoelectric substrate. This process is implemented primarily through lift-off and etching, both of which involve the steps of photolithography, metallization, and lift-off.

[0003] For the stripping process, after stripping the graphic layer, the steps of overlay bonding area, sputtering temperature compensation film, chemical mechanical polishing and stripping again are carried out. The main disadvantage of such process steps is that since the temperature compensation film is deposited by magnetron sputtering equipment, it is relatively dense and not conducive to stripping. If the overlay photoresist has not been stripped when the temperature compensation film is deposited, it is necessary to carry the photoresist into the sputtering chamber. However, the photoresist is an organic matter. Under the influence of plasma and heating, the organic matter in the photoresist will volatilize into the vacuum chamber, resulting in high-purity target material and chamber lining being contaminated, affecting the purity of the subsequent deposited film and the service life of the target material.

[0004] The etching process involves directly sputtering a temperature-corrected film after stripping the pattern layer, followed by chemical mechanical polishing, overlaying the bonding area, and finally wet or dry etching. The main drawbacks of this process are that dry etching equipment is expensive, and the etching gases are generally unhealthy for the environment and human health. Wet etching requires the use of hydrofluoric acid, which is also unhealthy for the environment and human health. Furthermore, there are relatively few types of photoresists resistant to hydrofluoric acid etching. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method of a temperature compensation filter and a temperature compensation filter.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] The present invention provides a method for preparing a temperature compensation filter, comprising the steps of plating a bonding area metal layer on a substrate, and overlaying photoresist on an area outside the bonding area metal layer through a mask; further comprising the steps of plating a thickened metal layer on the area where the bonding area metal layer is plated and the area where the photoresist is overlaid; stripping the photoresist and the thickened metal layer thereon; sputtering a temperature compensation film on the thickened metal layer and the area after the photoresist is stripped; and flattening the temperature compensation film to expose the thickened metal layer outside the temperature compensation film.

[0008] Furthermore, in the step of overlaying the photoresist, the thickness of the photoresist is greater than the sum of the thicknesses of the bonding area metal layer and the thickened metal layer.

[0009] Furthermore, the thickness of the temperature compensation film is greater than or equal to the sum of the thicknesses of the bonding area metal layer and the thickened metal layer.

[0010] Furthermore, the thickness of the temperature compensation film is 2 μm, and the sum of the thicknesses of the bonding area metal layer and the thickened metal layer is 1.6 μm.

[0011] Furthermore, the bonding area metal layer is plated on the substrate by using a graphic photoresist to photoetch a graphic layer on the substrate, and the graphic layer partially covers the substrate; a metal film is plated on the substrate after the graphic layer is photoetched; the graphic layer and the metal film covering the graphic layer are peeled off, and part or all of the metal film that has not been peeled off is the bonding area metal layer.

[0012] Furthermore, the thickness of the pattern layer is greater than the thickness of the metal film.

[0013] Furthermore, the step of photolithography pattern layer and the step of overlay respectively include coating, pre-baking, exposure, post-baking and development.

[0014] Furthermore, before implementing the photolithography pattern layer on the substrate, the substrate is first cleaned; the cleaning method includes one of cleaning with an electronic cleaning agent, cleaning with an ultrasonic device, cleaning with a brush, and cleaning with high-pressure deionized water.

[0015] Furthermore, the metal film coating and the thickened metal layer coating on the bonding area metal layer are both performed using an electron beam evaporation table.

[0016] The present invention provides a temperature compensation filter, which is prepared by adopting the above-mentioned method for preparing the temperature compensation filter.

[0017] The beneficial effects of the temperature compensation filter of the present invention are:

[0018] 1) In the preparation method of the present invention, the overlay step is arranged before the steps of plating a thickened metal layer and sputtering a temperature compensation film on the bonding area metal layer, which can avoid the need for further processing using an etching process, effectively reducing the cost of the preparation method and avoiding pollution to the environment.

[0019] 2) The preparation method of the present invention is to strip the overlay photoresist before sputtering the temperature compensation film; this can effectively avoid the problem of the temperature compensation film being difficult to strip, making the preparation method simpler;

[0020] 3) In the preparation method of the present invention, when sputtering the temperature compensation film, since there is no photoresist, there is no need to deliberately lower the process temperature during sputtering. The performance of the temperature compensation film can be improved by increasing the process temperature, thereby effectively improving the performance of the temperature compensation filter.

[0021] 4) The preparation method of the present invention, by plating a thickened metal layer on the metal layer of the bonding area, can prevent the problem of inaccurate bonding area after planarization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 2 is a schematic structural diagram of step 2) in an embodiment of the method for preparing a temperature compensation filter of the present invention;

[0023] Figure 2 1 is a schematic structural diagram of step 3) in an embodiment of the method for preparing a temperature compensation filter of the present invention;

[0024] Figure 3 4 is a schematic structural diagram of step 4) in an embodiment of the method for preparing a temperature compensation filter of the present invention;

[0025] Figure 4 1 is a schematic structural diagram of step 5) in an embodiment of the method for preparing a temperature compensation filter of the present invention;

[0026] Figure 5 Schematic diagram of the structure of step 6) in an embodiment of the method for preparing a temperature compensation filter of the present invention;

[0027] Figure 6 1 is a schematic structural diagram of step 7) in an embodiment of the method for preparing a temperature compensation filter of the present invention;

[0028] Figure 7 1 is a structural diagram of step 8) in an embodiment of the method for preparing a temperature compensation filter of the present invention;

[0029] Figure 8 FIG. 1 is a structural diagram of step 9) in an embodiment of the method for preparing a temperature compensation filter of the present invention.

[0030] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0031] 1. Substrate; 2. Bonding area metal layer; 21. Thickened metal layer;

[0032] 3. Overprinting layer; 4. Temperature compensation film; 5. Graphic layer. DETAILED DESCRIPTION

[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0034] The method for preparing a temperature compensation filter of the present invention comprises the steps of plating a bonding area metal layer 2 on a substrate 1 and overlaying a photoresist on an area outside the bonding area metal layer 2; further comprising the steps of plating a thickened metal layer 21 on the bonding area metal layer 2; stripping the overlaid photoresist; sputtering a temperature compensation film 4 on the thickened metal layer 21 and other areas; and flattening the temperature compensation film 4 so that the thickened metal layer 21 is exposed outside the temperature compensation film 4.

[0035] The preparation method of the present invention arranges the overlay step before the step of plating the thickened metal layer 21 and sputtering the temperature compensation film 4 on the bonding area metal layer 2, which can avoid the need for further processing using the etching process, effectively reducing the cost of the preparation method and avoiding pollution to the environment.

[0036] Before the step of sputtering the temperature compensation film 4, the overlay photoresist is first stripped off; since the temperature compensation film 4 is deposited by a magnetron sputtering device, it is relatively dense and not conducive to stripping. Setting the step of stripping off the overlay photoresist before sputtering the temperature compensation film 4 can effectively avoid the problem that the temperature compensation film 4 is difficult to strip off, making the preparation method simpler; at the same time, since there is no photoresist, there is no need to deliberately lower the process temperature during sputtering, and the performance of the temperature compensation film 4 can be improved by increasing the process temperature, thereby effectively improving the performance of the temperature compensation filter.

[0037] In the temperature compensation filter, the bonding area metal layer 2 is an area used for bonding with other components. The bonding area metal layer 2 is metal and needs to be exposed outside the temperature compensation film 4. After the metal film is plated, the distribution area of ​​the metal film on the substrate 1 is the same as the graphic layer 5. That is to say, in the distribution area of ​​the metal film at this time, a part of it needs to be exposed outside the temperature compensation film 4 as the bonding area metal layer 2 in the final temperature compensation filter, and a part of the metal film needs to be covered by the temperature compensation film 4. Therefore, if the thickness of the bonding area metal layer 2 is the same as that of the metal film in the non-bonding area, the metal film in the non-bonding area will also be easily exposed, resulting in inaccuracy of the bonding area metal layer 2. Therefore, a thickening process of the metal film of the bonding area metal layer 2 is added between the overlay step and the step of stripping the overlay photoresist, and a thickened metal layer 21 is plated on the bonding area metal layer 2 to prevent the above situation from occurring.

[0038] Preferably, in the step of overlaying the area outside the bonding area metal layer 2 with overlay photoresist, the thickness of the overlay photoresist is greater than the sum of the bonding area metal layer 2 and the plated thickened metal layer 21 .

[0039] It should be noted that the overlay process used in this method is a conventional overlay method. Specifically, a mask corresponding to the area to be overlaid is first prepared, and then overlay is performed using an overlay photoresist. In this method, the mask used for overlay can cover the metal layer in the bonding area, leaving the non-bonding area exposed. This allows the photoresist to adhere to the non-bonding area during overlay.

[0040] Preferably, the thickness of the temperature compensation film 4 is greater than or equal to the sum of the thicknesses of the bonding area metal layer 2 and the thickened metal layer 21 .

[0041] The present invention is exemplified and specifically described below by way of examples:

[0042] like Figures 1 to 8 As shown, the method for preparing the temperature compensation filter of this embodiment includes the following steps:

[0043] 1) First, the substrate 1 is cleaned; the cleaning method includes one of cleaning with an electronic cleaning agent, cleaning with an ultrasonic device, cleaning with a brush, and cleaning with high-pressure deionized water.

[0044] In this embodiment, ultrasonic equipment is used for cleaning, and the substrate 1 is dried after cleaning.

[0045] 2) Photolithography of a pattern layer 5 on the substrate 1 using a pattern photoresist, wherein the pattern layer 5 partially covers the substrate 1;

[0046] The steps of photolithography pattern layer 5 mainly include coating, pre-baking, exposure, post-baking and development.

[0047] In this embodiment, a commercially available photoresist is used, the spin speed is 3000 rpm, the pre-bake temperature is 94° C., the pre-bake time is 2 min, the exposure time is 380 ms, the post-bake temperature is 94° C., and the development time is 8 s.

[0048] In this embodiment, the thickness of the pattern layer 5 needs to be higher than the thickness of the metal layer 2 in the bonding area.

[0049] 3) A metal film is plated on the pattern layer 5 and on the substrate 1 not covered by the pattern layer 5 .

[0050] In this embodiment, Ti, Cu, and Al in the metal film are deposited by an electron beam evaporation station to achieve the metal film plating process.

[0051] 4) Peeling off the pattern layer 5 and the metal film covering the pattern layer 5. Among the metal films that are not peeled off, the metal film close to the edge of the substrate 1 is the bonding area metal layer 2.

[0052] After the metal film is deposited in step 3), it is immersed in a photoresist stripping solution and later stripped using a stripping machine.

[0053] 5) Make a mask corresponding to the bonding area and cover the substrate 1 with the mask, so that the non-bonding area is exposed and the bonding area is covered; use photoresist to overlay the area outside the metal layer 2 of the bonding area to obtain an overlay layer 3.

[0054] The steps of overlay etching mainly include coating, pre-baking, exposure, post-baking and development.

[0055] In this embodiment, another commercially available overlay photoresist is used, the overlay photoresist rotation speed is 5000 rpm, the overlay pre-baking temperature is 94°C, the overlay pre-baking time is 2 minutes, the overlay exposure time is 10 seconds, the overlay post-baking temperature is 94°C, the overlay post-baking time is 2 minutes, and the overlay development time is 18 seconds.

[0056] The thickness of the overlay layer 3 is greater than the sum of the thicknesses of the bonding area metal layer 2 and the thickened metal layer 21 .

[0057] 6) A thickened metal film is plated on the photoresist and the metal layer 2 in the bonding area to thicken the metal layer 2 in the bonding area.

[0058] In this embodiment, an electron beam evaporation station is used to deposit Al in the thickened metal film to achieve the process of plating the thickened metal film; the sum of the thickness of the bonding area metal layer 2 and the thickened metal layer 21 is 1.6 μm.

[0059] 7) Stripping off the overlay layer 3 and the thickened metal film covering it; immersing them in a photoresist stripping solution and stripping them off later.

[0060] 8) Sputtering a temperature compensation film 4 on the substrate 1 outside the thickened metal layer 21; depositing SiO2 of the temperature compensation film 4 by magnetron sputtering equipment. In this embodiment, the deposited thickness is 2 μm.

[0061] 9) Performing a planarization process on the temperature compensation film 4.

[0062] In this embodiment, the surface of the temperature compensation film 4 is processed by chemical mechanical polishing to expose the thickened metal layer 21 for bonding.

[0063] In this embodiment, finally, the sum of the thicknesses of the temperature compensation film 4 , the bonding area metal layer 2 , and the thickened metal layer 21 is equal to each other, which is 1.6 μm.

[0064] The temperature compensation filter prepared by the above method of this embodiment has the same or even better performance as commercially available temperature compensation filters.

[0065] In this embodiment, substrate 1 is specifically a lithium niobate substrate. The temperature compensation filter fabricated using the above method has a frequency of approximately 1000 MHz and a temperature drift coefficient of -15 ppm. These performance figures are comparable to those of similar commercially available temperature compensation filters, demonstrating that both have similar functional characteristics.

[0066] Therefore, the temperature compensation filter prepared by the preparation method of the present invention has functional characteristics similar to those of the same type of temperature compensation filters available on the market. This method simplifies the process steps, reduces the difficulty and cost of process implementation, and avoids pollution to the environment.

[0067] In summary, the preparation method of the present invention has the advantages of simple operation, low cost, and no pollution. Because the method of the present invention does not require reducing the temperature during sputtering of the temperature compensation film 4, the performance of the temperature compensation film 4 can be effectively improved, thereby effectively improving the performance of the temperature compensation filter prepared using the preparation method of the present invention.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a temperature compensation filter, characterized in that: The following steps are involved: 1) First, the substrate (1) is cleaned; the cleaning method includes one of cleaning with an electronic cleaning agent, cleaning with an ultrasonic device, cleaning with a brush, and cleaning with high-pressure deionized water; 2) using a pattern photoresist to photoetch a pattern layer (5) on the substrate (1), wherein the pattern layer (5) partially covers the substrate (1); The steps of the photolithography pattern layer (5) include coating, pre-baking, exposure, post-baking and development; A commercially available photoresist was used, with a spin speed of 3000 rpm, a pre-bake temperature of 94°C, a pre-bake time of 2 minutes, an exposure time of 380 milliseconds, a post-bake temperature of 94°C, and a development time of 8 seconds. The thickness of the graphic layer (5) is greater than the thickness of the bonding area metal layer (2); 3) coating a metal film on the pattern layer (5) and on the substrate (1) not covered by the pattern layer (5); The process of metal film coating is achieved by depositing Ti, Cu and Al in the metal film through an electron beam evaporation station; 4) peeling off the pattern layer (5) and the metal film covering the pattern layer (5), wherein the metal film that has not been peeled off and is close to the edge of the substrate (1) is the bonding area metal layer (2); After the metal film is deposited in step 3), it is immersed in a photoresist stripping solution and then stripped using a stripper; 5) making a mask corresponding to the bonding area, and covering the substrate (1) with the mask; using photoresist to overlay the area outside the metal layer (2) of the bonding area to obtain an overlay layer (3); The steps of overlay are coating, pre-baking, exposure, post-baking and development; Another commercially available overlay photoresist was used, with a spin speed of 5000 rpm, a pre-bake temperature of 94°C, a pre-bake time of 2 min, an exposure time of 10 s, a post-bake temperature of 94°C, a post-bake time of 2 min, and a development time of 18 s. The thickness of the overlay layer (3) is greater than the sum of the thicknesses of the bonding area metal layer (2) and the thickened metal layer (21); 6) performing a thickening process on the bonding area metal layer (2): plating a thickened metal film on the photoresist and the bonding area metal layer (2) to obtain a thickened metal layer (21); An electron beam evaporation station is used to deposit Al in the thickened metal film to achieve the process of plating the thickened metal film; the sum of the thickness of the bonding area metal layer (2) and the thickened metal layer (21) is 1.6 μm; 7) peeling off the overlay layer (3) and the thickened metal film covering it; immersing them in a photoresist stripping solution and then stripping them off; 8) sputtering a temperature compensation film (4) on the substrate (1) outside the thickened metal layer (21); depositing SiO2 on the temperature compensation film (4) by magnetron sputtering equipment, with a deposition thickness of 2 μm; 9) performing a planarization process on the temperature compensation film (4); The surface of the temperature compensation film (4) is treated by chemical mechanical polishing to expose the thickened metal layer (21) for bonding; Finally, the sum of the thicknesses of the temperature compensation film (4), the bonding area metal layer (2), and the thickened metal layer (21) is equal to 1.6 μm.

2. A temperature compensation filter, characterized in that: The temperature compensation filter is prepared by the method for preparing a temperature compensation filter according to claim 1.

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